John Brunner 
(Compleat) Traveller in Black [EPUB ebook] 

The time was the unguessably remote past – or perhaps the distant future. Throughout the universe, Chaos ruled. Scientific laws of cause and effect held no force; men could not know from one day to the next what to expect from their labours, and even hope seemed foolish.In this universe there was one man to whom had been entrusted the task of bringing reason and order out of Chaos. He was a quiet man dressed in black who carried a staff made of light, and wherever he went the powers of Chaos swirled around him, buffeted him, tested him. He fought them, and little by little he drove them back.But the Traveller in Black himself belonged to the anti-science universe. If he succeeded in his task of changing the order of the cosmos, could he continue to live?(First published 1971)